ISSN:
0947-6539
Keywords:
chalcogen compounds
;
metallocenes
;
selenium compounds
;
tellurium compounds
;
titanium complexes
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Permethyltitanocene hydride, [Cp*2TiH], reacts with elemental selenium or tellurium to give the products [(Cp*2Ti)2(μ-E)] (E = Se, 1a Te, 1b), [Cp*2Ti(μ2-E2)] (E = Se, 2a; Te, 2b) and [Cp*2Ti(μ2-Se3)] (3), depending on the equivalency of the chalcogen employed. Dinuclear compounds 1 are paramagnetic and have D2d (idealized) structures, as shown by X-ray structural analysis of μ-telluride 1b; they may be converted to diamagnetic dichalcogenides 2 through further reaction with the appropriate chalcogen. Derivatives 2 are monomeric in the solid state, as shown by X-ray structural analysis of ditelluride 2b, and in solution, as demonstrated by multinuclear NMR spectroscopy. Combination of diselenide 2a and ditelluride 2b results in partial redistribution to the mixed species [Cp*2Ti(μ2-SeTe)], suggesting dimeric structures of formula [Cp*2Ti(μ-E-E)2 TiCp*2] may be accessible in solution. The dichalcogenides and the triselenide may be converted back to complexes 1 by treatment with a chalcogen-abstracting agent. The possible involvement of monomeric terminal chalcogenides [Cp*2Ti(E)] in the interconversion of 1 and 2 was probed experimentally and computationally by means of Density Functional Theory calculations on [Cp2M(E)] (M = Ti, E = O, S, Se, Te; M = Zr, E = O, Te). Several unsuccessful attempts to generate and trap [Cp*2Ti(Te)] are described. The results of these studies suggest that [Cp*2Ti(Te)] has a very weak Ti-Te bond and a readily accessible triplet excited state. These factors, along with the small size of titanium, render this member of the [Cp*2M(E)] family of complexes difficult to trap with Lewis bases, in contrast to many other congeners in the series of Group 4 terminal chalcogenides.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/chem.19960021007
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